System and method for improved material processing using a laser beam

ABSTRACT

A method and system for improved material processing using a laser beam. The method and system includes directing a laser beam above, at or below the surface of the material in one or more preferred patterns and with preferred laser pulse characteristics specific to the material to reduce or mitigate the accumulation or effects of gas, debris, fluid, or other by-products of photodisruption either at the location where additional laser pulses are being placed or in other sensitive locations in the material.

RELATED APPLICATIONS

[0001] This application claims priority to U.S. provisional patentapplication 60/367,119 filed Mar. 23, 2002.

FIELD OF THE INVENTION

[0002] The present invention pertains generally to the field of materialprocessing with a laser beam and more particularly to systems andmethods for improved processing of these materials. The presentinvention is particularly useful for material processing utilizing laserphotodisruption as a mechanism of action, particularly when suchprocessing involves the use of multiple laser pulses placed on or belowthe surface of a material. While the field of the invention is verywide, it is particularly useful as a system and method for utilizing alaser beam to form a series of overlapping photodisrupted areas inside amaterial to define a new internal surface so that the anterior portionof the material can be moved to have access to the new internal surfaceof the material. A particular example of this application is in a typeof ophthalmic surgery for correcting a patient's vision by removing atleast a portion of an outer layer of the cornea. By creating a newinternal surface within the bulk of the corneal tissue, this procedureexposes underlying internal corneal tissue that can be altered toreshape the cornea and improve the patient's vision.

BACKGROUND OF THE INVENTION

[0003] There are three main classes of laser-material interaction:photocoagulation, photoablation, and photodisruption. Photocoagulationemploys continuous wave laser light applied to absorbing materialtargets, with effects mediated by primary and secondary effects ofthermal damage. This technique is most widely used in the eye to treatretinal diseases, such as diabetic retinopathy and macular degeneration.In photoablation, highly absorbing ultraviolet wavelengths are used tovaporize superficial materials, primarily for surface etching andrefractive surgical applications in the cornea.

[0004] Photodisruption begins with laser induced optical breakdown(LIOB), when a laser pulse generates a high intensity electric field,leading to the formation of a mixture of free electrons and ions thatconstitutes the plasma state. The hot plasma expands displacingsurrounding material. As the plasma expansion slows, the displacementfront propagates through the material as a shock wave. The shock waveloses energy and velocity as it propagates, relaxing to an ordinaryacoustic wave. The adiabatically expanding plasma quickly recombines andcools down, eventually forming a cavitation bubble. The constituents ofthe cavitation bubble depend on the make-up of the target material. Fororganic substrates, the cavitation bubble consists mainly of CO₂, N₂ andH₂O.

[0005] Using a photodisruptive laser and a delivery system, localizedphotodisruptions can be placed at or below the surface of a material toproduce high-precision material processing. In one example of suchmaterial processing, internal surfaces can be created within thematerial by placing multiple pulses along a predetermined path. Inspecial cases, these surfaces can be represented as planes placed in anyorientation to create horizontal, vertical or oblique effects.

[0006] In using photodisruptive lasers, variable outcomes can resultfrom the disposition of gas, debris, and other photodisruptiveby-products. In some materials, photodisruption results in formation ofgas and water vapor. The behavior and effects of these and otherby-products depend on the properties of the material surrounding them,as well as on the influence of additional laser pulses placedsubsequently in the near vicinity. Generally, a gas bubble expands insize into the area of least resistance. With expansion, the gas coolsand constituent gases, such as water vapor, can return to a liquidstate. The presence of gas, liquid, debris and other by-products createdduring photodisruption in the region where additional laser pulses arebeing placed can be a cause of variable or undesired outcomes. Thecurrent invention represents an improvement over previous techniquesutilizing laser photodisruption by offering elimination or mitigationstrategies against these potential influences.

[0007] A specific application of the invention is in the use of aphotodisruptive laser for the creation of a corneal layer in ophthalmicsurgical procedures to correct vision errors. Vision impairment canoccur for many reasons, and be the result of many causes. One commoncause for vision impairment results from a defective condition of theeye which occurs when the refractive characteristics of the cornea donot cause parallel rays of light to focus on the retina. When the eye isat rest, and the rays of light focus in front of the retina, thecondition is known as myopia (i.e. near-sightedness). On the other hand,when the rays of light focus behind the retina, the condition is knownas hypermetropia or hyperopia (i.e. farsightedness). Both myopic andhyperopic conditions result in varying degrees of vision impairment. Inmost cases the conditions are correctable.

[0008] Eyeglasses or contact lenses are commonly used to correct myopicor hyperopic conditions. For various reasons, however, many persons whosuffer with these conditions prefer not to wear eyeglasses or contactlenses. Alternative ways to correct these conditions include knownsurgical procedures for reshaping the cornea in various ways that areeffective in changing its refractive characteristics. For example, inU.S. Pat. Nos. 4,665,913 and 4,669,466 to L'Esperance, a laser system isdescribed which photoablates corneal tissue from the anterior surface ofthe eye. Another procedure is described in U.S. Pat. No. 4,988,348 toBille, whereby corneal tissue is first removed to correct vision, andthen the newly created surface is smoothed.

[0009] Rather than remove and reshape portions of the anterior portionof the eye to correct refractive defects, other procedures have beendeveloped using a technique called intrastromal photodisruption forremoving internal stromal tissue. Examples of such procedures and lasersystems are described in U.S. Pat. No. 4,907,586 to Bille et al and U.S.Pat. No. 5,993,438 to Juhasz et al. Another example of a procedure forremoving stromal tissue is the procedure described in U.S. Pat. No.6,110,166 to Juhasz. In this procedure, an anterior corneal layer can bedefined by using a laser to create a series of overlappingphotodisrupted areas. The surgeon then separates the corneal layer bylifting it, to gain access to the underlying corneal tissue, the shapeof which is changed with a photoablative laser, such as an excimerlaser. The corneal layer is then repositioned on the cornea.

[0010] In prior practice, surgeons would create a corneal layer byfocusing the laser beam at a starting point at or near the center of theto-be-formed corneal layer. The laser beam begins photodisrupting areasof tissue at the starting point, and is moved along a predeterminedpath, typically in a spiral pattern, from the center of the corneallayer to a predetermined circumference of the corneal layer. Finally,the laser beam is directed around the predetermined circumference toform a peripheral cut from the corneal layer to the outer surface of thecornea.

[0011] It has been observed in some cases that moving the laser beamalong a predetermined path or pattern creates a temporary cloudyappearance, which is believed to result from gas and/or debris createdduring the photodisruption process that spreads inside the tissuebecause there are no outlets for the gas and debris. This condition istemporary; the gas and/or debris are eventually absorbed in surroundingtissue after a few minutes. Although this condition has no signficantside effects, spread of gas can influence the effectiveness of furtherlaser pulses placed in the predetermined path in creating a high qualityinternal surface. Both the cloudy appearance and the less effectiveeffects of ensuing laser pulses are considered undesirable.

[0012] It has also been observed that, in some cases and situations,moving the laser beam along a predetermined pattern creates fluid thatcan spread in the tissue and influence the effectiveness of furtherlaser pulses placed in the predetermined path in creating a high qualityinternal surface. This fluid may result in surface irregularities thatreduce the smoothness of the newly-created internal surface.

[0013] Thus, there is a perceived need for a predetermined path orpattern that does not cause gas and debris to spread in the tissue, orthat does not lead to the above described creation or spread of fluid,both of which alter the character and effectiveness of further pulsesplaced along the predetermined path. As an alternative, even if thesegas and/or fluid effects cannot be eliminated, the impact of thesenegative secondary effects also can be mitigated by choosing specificpredetermined paths. Additionally, a need exists for a method and systemto implement these desirable photodisruption patterns and predeterminedpaths.

[0014] A specific example of a desirable pattern or predetermined pathinvolves creation of a secondary pattern or predetermined path connectedor adjacent to the primary pattern or predetermined path. This reservoircan control the effects of by-products and/or gas from any type ofpattern cut. Additionally, a need exists for a method and system toimplement the reservoir. In conjunction with such a reservoir, or as analternative approach, specific laser pulse placements andcharacteristics in the primary or secondary pattern or predeterminedpath can be chosen to control the effects of by-products and/or gas fromany type of pattern cut.

SUMMARY OF THE INVENTION

[0015] In accordance with the present invention, a method and systemhave been developed for improved material processing usingphotodisruptive lasers. The method includes the steps of directing alaser beam at a starting point above, at or below the surface of amaterial and thereafter moving the laser beam from the starting pointalong a preferred predetermined path to reduce or mitigate effects ofgas, debris and other by-products created during photodisruption in theregion where additional laser pulses are being placed.

[0016] In one embodiment of the present invention, the preferredpredetermined path has a starting point in a particular region of thematerial that reduces or mitigates effects of gas, debris and otherby-products created during photodisruption in a more critical region ofthe material. As an example of this embodiment, the predetermined pathmay begin at the circumference of the pattern to be placed on or in thematerial to reduce or mitigate effects of gas, debris and otherby-products created during photodisruption in the center of the pattern.Examples of this embodiment include moving the focal point along apredetermined path in a spiral pattern that starts at the predeterminedcircumference of the internal surfaces and runs toward the center of thepredetermined circumference. In another embodiment, the predeterminedpath is in the shape of a raster pattern that runs back-and-forththrough the material from a starting point near the predeterminedcircumference toward the opposite side of the predeterminedcircumference. In a third embodiment, the focal point of the laser beamis moved along a predetermined path in the shape of a series ofconcentric circles that runs from the starting point at or near thepredetermined circumference toward the center of the predeterminedcircumference. While these embodiments localize the effects of gas,debris, and other by-products created at the start of photodisruption tothe circumference of a pattern, the opposite effect can be chosen bychoosing a starting point at the center of a pattern.

[0017] In another embodiment of the invention, material processing canbe influenced through creation of a secondary pattern (with its ownpreferred pattern or predetermined path), that is connected or adjacentto the primary predetermined path. Gas, debris and other by-productscreated during photodisruption in the primary predetermined path can besignificantly reduced or eliminated from the region of further laserpulse placement through creation of these so-called reservoirs.

[0018] In another embodiment of the invention, the effects of createdsecondary patterns can be optimized by choosing specific geometries andinternal laser pulse characteristics, that may be different from thoseof the primary pattern. These include the area, depth, laser pulse topulse distance (spot separation) and energy.

[0019] In another embodiment of the invention, material processing canbe influenced by naturally occurring reservoirs in the material, if theyallow the collection of gas, debris and other by-products created duringphotodisruption in the primary predetermined path. Secondary patterns orpaths can be created to connect these naturally occurring reservoirs,with the effects on the primary pattern or path influenced by selectionof specific geometries and internal laser pulse characteristics forthese connecting patterns, which may be different from those of theprimary pattern. These include the area, depth, laser pulse to pulsedistance (spot separation) and energy.

[0020] In another embodiment of the invention, in the presence of aneffectively operating reservoir, the specific laser pulsecharacteristics of the primary pattern or predetermined path can bechosen to reduce or mitigate effects of gas, debris and otherby-products created during photodisruption in the area of further laserpulse placement. These include the area, depth, laser pulse to pulsedistance (spot separation) and laser pulse energy.

[0021] When the material is the cornea of the eye and the goal iscreation of a corneal layer, the predetermined path runs through thestromal tissue to define the corneal layer. An anterior internal surfacecan be formed with or without a hinge between the anterior internalsurface and the peripheral cornea. The starting point of the primarypredetermined path can be located either beneath the outer surface ofthe cornea or on the outer surface of the cornea. The predetermined pathcan be shaped such that the primary predetermined circumference isformed in a variety of shapes, for example generally circular orgenerally oval-shaped. The primary predetermined path can also be shapedsuch that the anterior internal surface is generally planar, generallyconvex, generally concave, or generally shaped to conform to the shapeof any underlying excimer laser ablation in the tissue below theanterior internal surface.

[0022] Another aspect of the invention is directed to exposing aninternal surface of the cornea with a predetermined circumference byforming a series of overlapping photodisrupted areas of stromal tissueto form a corneal layer, which has an anterior surface and a posteriorsurface. This corneal layer is at least partially removable from thecornea. The method includes the steps of positioning a focal point of alaser beam at a starting point in the vicinity of the predeterminedcircumference of the internal surface and photodisrupting tissue at thestarting point, then moving the focal point of the laser beam from thestarting point along a predetermined path and photodisrupting tissuealong the path to create a pattern of overlapping areas across theinternal surface to be exposed to form the corneal layer, and removingat least a portion of the corneal layer to expose the internal surfaceof the cornea. Additional embodiments of this aspect of the inventionare similar to the ones described herein.

[0023] The method can also include the step of forming a peripheralsurface that extends at an angle from the posterior internal surface tothe outer surface of the cornea. The peripheral surface is formed bymoving the focal point of the laser beam and photodisrupting tissue at aplurality of points along a path that runs from the vicinity of theanterior internal surface to the outer surface of the cornea. In oneembodiment, the peripheral surface is formed at an angle of equal to orgreater than 90 degrees relative to the posterior internal surface,while in another embodiment the peripheral surface is formed at an angleof less than 90 degrees relative to the posterior internal surface.

[0024] In the case of the creation of a corneal layer, gas in theinterface where laser pulses are being placed can create interruptedareas of separation between the two surfaces. Liquid in the interfacecan create uneven surfaces. The former can occur when resistance is highin the horizontal location adjacent to the forming gas bubble, causinggas to spread in the cornea through spaces in the cornea, creatingextraneous bubbles. If resistance is low in the horizontal locationadjacent to the forming gas bubble, gas spreads horizontally and noextraneous bubbles are seen. The latter can occur if resistance is verylow in the horizontal location adjacent to the forming gas bubble, thengas spreads very quickly, leading to rapid cooling and condensation ofwater vapor. This fluid can then seep back into the interface of theregion where laser pulses are being placed. The presence of fluid in theinterface of the region where laser pulses are being placed can resultin a local depth change and the production of large feature surfaceabnormalities, such as ridges and waves.

[0025] In the case of creation of a corneal layer, a reservoir orsecondary pattern or predetermined path can be optimized with thefollowing parameters to reduce gas bubbles and improve corneal layerformation: larger reservoir area, greater depth, higher laser pulseenergy, and closer spot separation. To reduce the effects of fluid inthe area where pulses are being placed, the opposite of the above schemecan be implemented.

[0026] In the case of creation of a corneal layer, the specific laserpulse characteristics of the primary pattern or predetermined path(i.e., the planar cut) can be optimized to reduce gas bubbles (andimprove corneal layer formation): decrease spot separation and laserpulse energy. To reduce the effects of fluid in the area where pulsesare being placed, the opposite of the above scheme can be implemented.

[0027] In the case of creation of a corneal layer, a reservoir and/orconnection may be formed extending from the posterior internal surfaceto the periphery of the cornea towards or to the corneal-scleraljunction (limbus). The reservoir may be at any angle to the posteriorsurface and can extend for any circumference or have any shape. Thisreservoir assists in the control of gas/liquid and debris accumulation.Additionally, the reservoir affects tissue separation/resectioncharacteristics. Also, the reservoir affects character/quality ofcreated surfaces for specific geometries and depth locations of theintended internal surface or surfaces that does not cause gas and debristo become trapped at the center portion of the removable layer. Althoughthe reservoir herein is discussed in the context of corneal tissue thereservoir may be utilized in other tissue or non-biologic material toassist in the removal of debris where a primary photodisrupted cut ismade.

[0028] The invention also includes a computer-readable medium havingsoftware embodied thereon to perform the steps described herein. In thecase of an ophthalmic surgical system, a computer system is provided fordirecting a laser beam to create the desired patterns and laser pulsecharacteristics. The system includes an input control device forreceiving the selection of a predetermined path from the user, a memoryfor storing a selection of predetermined paths, a processor unit coupledto the input control device and to the memory for processing theinformation inputted by the user to identify the selected predeterminedpath and performing the step of controlling the movement of the laserbeam along the selected predetermined path, an output display fordisplaying the progress of the method, a laser source having the abilityto focus and disrupt material above, at or below the corneal surface,and a focusing or directing mechanism for the laser source that iscoupled to the processor unit and output display.

[0029] The invention also includes a femtosecond laser system thatincludes a laser source for generating a laser beam having the abilityto focus and disrupt material above, at or below the surface and aprocessor for directing the laser beam to create a desired pattern. Thesystem performs the steps of directing the focal point of the laser beamto a starting point, moving the focal point along a preferredpredetermined path such that the effects of gas, debris and otherby-products created during photodisruption are reduced or mitigated inthe region where additional laser pulses are being placed. Anotheraspect of the invention is computer-implemented method for directing alaser beam to create a preferred predetermined path above, at or belowthe surface a material. A selection of a geometric border for a patterncut is selected by a user or read from a file or database and receivedby the software where the selected geometric border parameter is storedinto memory. The geometric border is displayed about an image of thematerial. A central point of the material may be determined for use inorienting the border about the material. The orientation is initiallydone programmatically; however, the user may reorient the geometricborder. The type of pattern cut is selected by the user or read from afile or database and received by the software where the selected type ofpattern cut is stored into memory. A laser beam is then directed toperform photodisruption of the material using the selected pattern cutfor the selected geometric border. The photodisruption ordinarily occursbelow the material surface based on a depth value. Among others, patterntypes may be concentric, spiral, and rasterized. The photodisruption maycreate a horizontal resection of the material. The laser beam may thenbe directed to create a vertical resection of the about thecircumference of the horizontal resection. A hinge may be created if thevertical resection is not made along the entire length of thecircumference of the geometric border.

[0030] As intended for the present invention, the laser system to beused for accomplishing the methods will incorporate a beam of sequentiallaser pulses. Further, it is contemplated that the duration of laserpulses in the beam will be in the nanosecond, picosecond or femtosecondranges.

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The novel features of this invention, as well as the inventionitself, both as to its structure and its operation will be bestunderstood from the accompanying drawings, taken in conjunction with theaccompanying description, in which similar reference characters refer tosimilar parts, and in which:

[0032]FIG. 1 is a perspective view of a patient being treated with themethod of the present invention;

[0033]FIG. 2 is a perspective view of an eye;

[0034]FIG. 3 is a cross-sectional view of the cornea of the eye as seenalong the line 4-4 in FIG. 2 showing the creation of an anteriorinternal surface and a posterior internal surface, or alternatively, acorneal layer;

[0035]FIG. 4 is a cross-sectional view of the cornea of the eye as seenalong the line 4-4 in FIG. 2 showing a removal of the anterior internalsurface and exposing the posterior internal surface, or alternativelyshowing a removal of the corneal layer, exposing the internal surface ofthe cornea;

[0036]FIG. 5 is a plan view of the cornea of the eye as seen in thedirection of the line 3-3 in FIG. 2 showing the path for movement of thelaser beam in a outward spiral pattern to create the anterior internalsurface and the posterior internal surface, or alternatively, thecorneal layer;

[0037]FIG. 6 is a plan view of the cornea of the eye as seen in thedirection of the line 3-3 in FIG. 2 showing a path for movement of thelaser beam in an inward spiral pattern to create the anterior internalsurface and the posterior internal surface, or alternatively, thecorneal layer;

[0038]FIG. 7 is a plan view of the cornea of the eye as seen in thedirection of the line 3-3 in FIG. 2 showing a path for movement of thelaser beam in a raster pattern to create the anterior internal surfaceand the posterior internal surface, or alternatively, the corneal layer;

[0039]FIG. 8 is a plan view of the cornea of the eye as seen in thedirection of the line 3-3 in FIG. 2 showing a path for movement of thelaser beam in a concentric-circle pattern to create the anteriorinternal surface and the posterior internal surface, or alternatively,the corneal layer;

[0040]FIGS. 9a and 9 b are plan views of the cornea of the eye as seenin the direction of the line 3-3 in FIG. 2 showing a path for movementof the laser beam to form the peripheral surface;

[0041]FIG. 10a and 10 b are plan views showing one embodiment of areservoir formed adjacent to a pattern cut; and

[0042]FIG. 11 is a plan view showing another embodiment of a reservoirformed adjacent to a pattern cut.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0043] Referring initially to FIG. 1, an apparatus 10 for generating alaser beam 12 is shown. The laser beam 12 is directed onto an eye 14 ofa patient 16. For purposes of the present invention, the apparatus 10 iscapable of generating a pulsed laser beam 12 having physicalcharacteristics similar to those of the laser beams generated by a lasersystem as disclosed and claimed in U.S. Pat. No. 4,764,930, which isexclusively licensed to the assignee of the present invention.Furthermore, the present invention contemplates the use of a pulsed:laser beam 12 which has pulses with durations as long as a fewnanoseconds or as short as only a few femtoseconds.

[0044] In one embodiment, a laser unit is controlled by software forphotodisruption of the cornea utilizing a laser beam of constant energy,composed of an optical train of pulses with a duration of approximately600 femtoseconds at a repetition rate of up to several hundred thousandHz. The actual energy in the emitted pulse train is determined byrotating a variable attenuator, an energy attenuation wheel, whichoperates under stepper motor control.

[0045] Energy measuring devices are placed in the optical path betweenthe attenuator and safety shutters. These devices measure a constantfraction of the energy transmitted to the optical delivery system. Theoptical delivery system consists of an articulated arm, Z-axis lift,X-axis and Y-axis translation, X, Y, Z-axis galvanometer scanners,telescope, Z-axis focusing lens, turning mirror, microscope and adisposable applanation lens that makes the contact with the patient'seye.

[0046] The optical delivery system determines a 3 -dimensional positionin the patient's cornea at which the laser is focused. When the laser ispulsed, the energy delivered to the point of focus is sufficient toionize tissue (photodisrupt) in a very small volume. Repetitivelysetting a focus point and pulsing the laser results in a resected planeof tissue.

[0047]FIG. 2 shows the anatomical structure of eye 14 and, specifically,that the cornea 18 is anterior to the pupil 20, the iris 22, and thesclera 24. Additionally, FIG. 2 indicates that the optical axis 26 ofeye 14 passes through the cornea 18. Consequently, the tissue of cornea18 is transparent to visible light.

[0048] In FIG. 3 it can be seen that the cornea 18 includes fiveanatomically definable layers of tissue. Going in a direction fromanterior to posterior in FIG. 3, the tissue layers of the cornea are:epithelium 26, Bowman's membrane 28, stroma 30, Decemet's membrane 32and endothelium 34. The anterior internal surface 35 and posteriorinternal surface 38 are created by focusing the focal point of a laserbeam at a predetermined starting point 42 and moving the focal point ofthe laser beam from the starting point 42 through the stromal tissue ina predetermined pattern to form a series of overlapping photodisruptedareas. Alternatively, a corneal layer 36 can be created in similarmanner.

[0049]FIG. 4 shows the anterior internal surface 35 or the corneal layer36 partially removed from the eye. The corneal layer 36 has an outersurface 37 that is the outer surface of the cornea. The corneal layer 36may be completely removed from the eye, or may remain attached at ahinge, as shown in FIG. 4. The corneal layer 36 can be removed, as shownin FIG. 4, to expose the internal surface of the cornea 39 that is to bephotoablated.

[0050] The pattern of movement of the laser beam is one aspect of thepresent invention. Referring to FIG. 5, in prior practice, surgeonswould choose a starting point 42 near the center of the corneal layerand move the laser beam in a pattern such as a spiral, working out tothe predetermined circumference. As mentioned above, however, it hasbeen observed in some cases that this pattern can create a cloudyappearance in the center of the corneal layer. The cloudy appearance isthe result of gas and debris that is created during the use of thelaser. Due to the central-to-circumference spiral pattern, this gas anddebris is trapped inside the cornea, as the outlets for the gas anddebris are limited. This cloudy appearance is undesirable and may reducethe effectiveness of additional laser pulses being placed. Conversely,when created gas has access to a created or naturally occurringreservoir, fluid can reach the area where additional laser pulses arebeing placed, thereby interfering with the tissue separation and leadingto an uneven surface.

[0051] The present invention minimizes the accumulation of the gas,fluid, debris and other by products in the area where additional laserpulses are being placed or in other sensitive areas of the materialundergoing processing. Referring to FIG. 6 for the case of the cornea,by selecting a starting point 42 below the surface of the cornea,substantially close to the predetermined circumference 43 of the corneallayer and moving the focal point of the laser beam along a pattern, suchas the circumference-to-central spiral pattern shown in FIG. 6, or theraster pattern shown in FIG. 7, or the concentric-circle pattern shownin FIG. 8, to an ending point 44, the accumulation of gas and debris isminimized in the center, which reduces the cloudy appearance. Thepredetermined circumference 43 of the corneal layer 36 may besubstantially in the shape of a circle or an oval. The figuresillustrate various embodiments of creating a pattern. The illustratedfigures are not meant to limit the patterns.

[0052] Note that in the concentric-circle pattern of FIG. 8, there willbe a separate starting point for each concentric circle. The firststarting point 42 is substantially close to the predeterminedcircumference 43 of the corneal layer. After the laser beam has beendirected on a circular path, it will come to an ending point 46,substantially close to the first starting point 42. Then, the laser beamis directed to a second starting point 48 and is moved along a circularpath to a second ending point 50, substantially close to the secondstarting point 48. This process is continued until the laser beam isdirected to a final starting point 52 and is moved along a circular pathto a final ending point 44, substantially close to the final startingpoint 52.

[0053] The predetermined path may be in a single plane, or may be a pathsuch that the anterior internal surface 35 or internal surface ofstromal tissue 39 is concave or convex.

[0054] After the laser beam has been moved along the predeterminedpattern, the laser is then directed to form a peripheral surface 45around the predetermined circumference 43 of the corneal layer 36 or theanterior and posterior internal surfaces that connects the outer surfaceof the cornea 37 to the anterior internal surface 35 of the corneallayer 36. Forming the peripheral surface 45, shown by the dashed linesin FIGS. 9a and 9 b, is accomplished by using the focal point of thelaser beam to create a series of overlapping photodisrupted areasbetween the predetermined circumference of the corneal layer or anteriorand posterior internal surfaces and the outer surface of the cornea, andcan be performed such that the peripheral surface 45 is at an anglerelative to the posterior internal surface 38. This angle can be greaterthan 90 degrees, such that the peripheral surface 45 and the posteriorinternal surface 38 form a bowl-shape, or it can be less than 90degrees, such that the peripheral surface 45 and the posterior internalsurface 38 form a conical-shape. To achieve an angle of greater than 90degrees, the focal point of the laser beam is first directed around thepredetermined circumference 43, and then is directed on a path ofsuccessively slightly larger circumferences, working toward the outersurface of the cornea. Conversely, to achieve an angle of less than 90degrees, the focal point of the laser beam is first directed around thepredetermined circumference 43, and then is directed on a path ofsuccessively slightly smaller circumferences working toward the outersurface of the cornea. To achieve an angle of exactly 90 degrees, thefocal point of the laser beam is first directed around the predeterminedcircumference 43, and then is directed on a path of the exact samepredetermined circumference, working toward the outer surface of thecornea.

[0055] The peripheral surface 45 may continue around the entirepredetermined circumference 43, as shown in FIG. 9a, or may bediscontinued before it has made a complete revolution around thepredetermined circumference 43, leaving part of the corneal layer 36 oranterior internal surface 35 attached at a hinge 54, forming a flap, asshown in FIG. 9b. After forming the peripheral surface 45, the surgeonmay remove the anterior internal surface 35 to expose the posteriorinternal surface 38 and finish the procedure. In the alternative aspectof the invention, the surgeon may remove the corneal layer 36 to exposethe internal surface of stromal tissue 36 and finish the procedure.

[0056] To further reduce the accumulation of gas, fluid, debris andother by-products in the primary pattern or predetermined path, asecondary pattern or reservoir can be created peripheral or adjacent tothe primary pattern to allow accumulation of gas and debris from theprimary treatment pattern. This reservoir can be created prior to thecreation of the main pattern in any shape and size, and preferablyshould connect to the main pattern either directly or through naturalpreexisting channels or potential channels in the cornea. Gas and debriscan accumulate in this reservoir or drain peripherally through existingpathways of the eye.

[0057] Creating a fluid (gas) communication between the reservoir andthe main pattern is preferred, but may not be necessary. Naturalchannels may serve the same purpose.

[0058] Providing a path or too easy a path for gas, fluid, debris andother by-products in the primary pattern or predetermined path may alsohave undesirable effects, because fluid can interfere in the regionwhere laser pulses are being placed. In one embodiment, the optimaltotal area of the reservoir is about 10% that of the total area of theprimary pattern cut. In another embodiment the pulse to pulse distancewithin the reservoir is greater than 6 microns and the pulse energy isless than 8 microjoules. In another embodiment, a small connectionbetween the main pattern and the reservoir may be used, the size ofwhich may further regulate effectiveness.

[0059] Increased drainage is a function of increased reservoir angle,increased reservoir diameter, and increased reservoir depth. Increasedneed for drainage is a function of increased area of the main patterncut, shallower depth of main cut, and higher pulse energy in the maincut (which causes more gas to be produced). To increase control ofdrainage, the size of the reservoir is decreased, and the internal“resistance” of the reservoir is increased by decreasing the pulseenergy and increasing the spot separation.

[0060] Referring to FIGS. 10a and 10 b, one embodiment of a reservoir 62is shown formed adjacent to a pattern cut 60. As exemplified, theprimary pattern 60 is made as a raster pattern for the horizontalresection. However, other patterns may be used for the primary pattern.The particular placement, width, depth, and angle of the reservoir aremade to accommodate the particular dimensions of the primary pattern. Areservoir 62 (also referred to as a pocket) is made adjacent to the mainpattern cut 60, which in this example has a radius of 4.1 mm. Thereservoir angle is 120° from about the central point of the eye. Thewidth of the reservoir is about 300 to 400 μm from the first arcposition 64 to the second arc position 65. The preferable pocket(reservoir) angle is 45-90 degrees, and the preferable maximum pocketwidth is 300 microns. The reservoir 62 is preferably formed first,before making the main pattern cut. The bottom of the reservoir is shownat about 160 μm from the surface of the cornea. The second arc positionis shown made adjacent to the limbus 61.

[0061] Referring now to FIG. 11, another embodiment of a reservoir 71 isformed adjacent to a pattern cut 70. In this embodiment, a complete 360°pocket circumscribing the horizontal resection 70 is created, but withinthe circumference of the limbus 73. In this example, the width of thereservoir is shown at about 100-200 μm. Preferably, the reservoir 71should be made first, then the primary pattern 70 made.

[0062] One manner to implement the method of the present invention is toprovide a laser unit with a computer system that directs a focal pointof a laser beam to perform the method described herein. The computersystem includes an input control device for receiving information fromthe user such as the selection of a predetermined pattern to be used inthe method, memory for storing a selection of predetermined patterns, aprocessor unit coupled to the input control device and to the memory forprocessing the information inputted by the user to identify the selectedpredetermined pattern, an output display for displaying the progress ofthe method, a laser source having the ability to focus and disrupttissue below the corneal surface, and a focussing mechanism for thelaser source that is coupled to the processor unit and output display.

[0063] Another manner to implement the method of the present inventionis to provide a software program that directs a focal point of a laserbeam to perform the methods described herein. One embodiment of such asoftware program is a program operable with an input control device andan output display device. The input control device may be a keyboard,mouse, touch screen or other input devices used with computers. Theoutput display device is a monitor or computer screen. The softwareprogram interacts with a database to store and retrieve data andparameters for the operation of the laser unit.

[0064] The software program, in addition to various otherfunctionalities, provides for a selection or determination of ageometric border of the pattern cut, orientation of the geometric borderover the cornea, direction of the laser beam movement, selection of typeof pattern cut, and selection of additional patterns.

[0065] Determining geometric border of the pattern. The software programuses a defined geometric border for the circumference of the horizontalresection. The border sets the outside boundaries of the horizontalresection pattern. The software application may be configured to useonly one geometric border, such as a circular border, as a standarddefault pattern. Alternatively, the software may be configured to allowthe operator of the laser unit to select from a set of availablegeometric borders. Multiple pattern segments may be combined to createspecial or non-uniform geometric borders, for creation of reservoirs anddrainage pathways. A user interface, typically a display monitor,presents the user with a selection of available geometric borders forhorizontal resections of the corneal tissue. If the operator wants toselect a different geometric border, the user selects a different borderfor the horizontal resection. For example, the software application maybe configured to use a circle as a standard default geometric shape forhorizontal resection. The laser unit operator, however, may select adifferent geometric border deciding that a different border, such as anoval, may be more advantageous for a particular patient.

[0066] Orienting the geometric border over the cornea. The geometricborder is displayed over an image of the patient's eye. This image maybe an actual image of the patient's eye, or a computer generated imageof the eye. The geometric border is positioned such that the center ofthe geometric shape is positioned over the central point of the eye. Thecentral point may be the visual axis of the eye at the surface of thecornea, or the symmetrical axis of the cornea, based on the center ofthe pupil.

[0067] The operator may move, rotate and resize the geometric border byinteracting with the graphical user interface (GUI). The GUI allows theoperator to graphically orient and position the border over theparticular portion of the cornea in which the horizontal resection willbe made. The software application may display zones or provide visual oraudible indicators if the geometric border is positioned in an areaoutside of the laser operating range. For example, the display may showa general area where the geometric border may be positioned. If thegeometric shape is positioned in an area not allowed forphotodisruption, then the laser source will not initiate the laser beam.

[0068] The geometric border has a defined portion where the flap hingeexists. This predefined portion indicates where no photodisruption ofthe geometric border will occur. The hinge is indicated to the operatorby a thicker and different color line than the rest of the border. Thelaser operator may graphically select a different side(s) or a portionof the geometric border where the hinge of the flap is to be made. Inother words, the operator may change the location of the hinge and/orthe length of the hinge. Also the operator may desire to remove thecorneal flap altogether. To do so, the operator, would select that nohinge be made.

[0069] The boundaries of the geometric border may be defined such thatthe circumference of the geometric border is set at a particulardistance from the center point. For example, if the shape is a circlethen a parameter for the radius may be predefined at 4 mm. The softwarewould determine the circumference from the center point. The creation ofthe vertical and horizontal resection would stay within or closely aboutthe determined circumference. If the operator wants to change theradius, then the geometric shape may be graphically resized by an inputdevice. Alternatively, the radius distance value may be entered via aninput device.

[0070] Controlling internal laser pulse parameters within scan pattern.The software may be used to alter internal pattern parameters, such asthe separation distance between pulses, pulse energy, and others for thepurpose of altering or varying the resection or gas/debris/fluidaccumulation characteristics of the overall pattern or affecting thecharacter of the created surfaces.

[0071] Directing laser movement The software application also allowscontrol of the movement of the laser focus spot. A standard spotdistance value is used by the software application for a particularlaser source. The spot distance value is the distance the laser moves inrelation to the previous spot made. Additionally, the softwareapplication uses a line separation value. For a raster pattern, thisvalue will control the movement over to the next line where the laserwill focus. For a concentric pattern a line separation value is used todetermine the placement of the next concentric ring in relation to theprevious concentric ring.

[0072] Selecting type of pattern cut. The software application providesthe laser operator a selection for type of pattern cut. The softwareutilizes the selected type of pattern cut to instruct the movement ofthe laser beam. In one embodiment, these patterns are spiral, concentricand raster. However, other patterns may be programmed, including, butnot limited to, variable reservoirs for peripheral movement oraccumulation of gas or debris and control of tissue resectionalseparation as well as characteristics of created surfaces.Alternatively, the application may have the pattern type preset, or thepattern selection type limited. The spiral pattern generally will causethe laser to photodisrupt the corneal tissue in a spiral patternbeginning from a center point. Preferably, however, the spiral patternbegins at a starting point about the predetermined circumference toabout a central point. The concentric pattern will cause the laser tophotodisrupt the corneal tissue in a concentric ring pattern beginningwith a central point and then photodisrupting in concentric rings aroundthe central point. Preferably, however, the concentric ring patternbegins at a starting point about the predetermined circumference toabout a central point.

[0073] The standard spot and/or line separations can be varied within aparticular pattern to control or influence the character of tissueresection/separation and/or accumulation or movement of gas or debris,as well as the character of created surfaces.

[0074] Selecting additional patterns. Additionally, the software programmay be configured to allow additional options for the horizontalresection. These options include: repeating the photodisruption selectedpattern using the same orientation, rotating the orientation of theselected pattern and repeating, after performing a first pattern forhorizontal resection, using a second pattern, or interstitial pattern. Arepeated pattern may use the same or different laser parameters, such asspot separation, energy per pulse, and depth.

[0075] Selecting Reservoir and Connecting Parameters. The softwareapplication provides the laser operator a selection to create areservoir or a connection to an existing reservoir. For example, beloware some parameters that may be used for reservoir or connectioncreation. The primary pattern parameters are controllable to optimizeuse of a particular reservoir geometry and internal structure bychanging spot separation, increasing or decreasing spot separation, orchanging geometry (size or position) of the main pattern. This is usefulwhen there are limitations as to placement of the reservoir.

[0076] For example, with the creation of a horizontal resection, aprimary pattern of the raster type is selected, a spot separation valueis set to 12, the line separation value is set to 10, the pulse energy Jvalue is set to 5, and the depth is set to 130 μm, and the diameter isset to 8.2 mm. In the creation of a reservoir, an arc scan is selected,with a 120° reservoir angle, a radial spot separation value of 9, atangential spot separation value of 7, pulse energy starts at 8 J andramps down to 5 J, reservoir start depth is 160 μm, and end depth is 130μm, the “width” of the reservoir is 300-400 μm. TABLE 1 ParameterExample Values for Example Values for Secondary Description PrimaryPattern or Reservoir Pattern Laser Pulse 1-10 μJ with ability 1-10 μJwith ability Energy to vary energy over to vary energy over the patternthe pattern Laser Pulse 2-20 microns Separation Shape Circular, ovalRing, Arc, variable Size 2-10 mm diameter Variable Depth VariableVariable Start Variable Variable Location

[0077] Example of Raster Pattern with a Circular Geometric Border. Thefollowing is an example of a flap created where a raster pattern hasbeen selected to be made within a circular geometric border. A centralpoint on the cornea is determined. This central point is given an Xvalue of zero and a Y value of zero. To make a raster cut for ahorizontal resection of stromal tissue, the focused laser begins at themaximum radius of the circular border at the most positive Y-axislocation. The laser source sends a laser pulse(s) to photodisruptcorneal tissue at the current X/Y coordinate at a Z-axis depth value(the depth of the focused laser beam).

[0078] An applanation lens, an example of which is described inco-pending application U.S. Pat. No. 09/772,539, may be used to flattenthe surface of the cornea to decrease or prevent spherical aberrationsand coma. Thus, the Z-axis depth value (the distance from the cornealsurface) for the horizontal resection may remain constant throughout thehorizontal resection. Using an applanation lens and keeping the Z-axisdepth value constant will result in resection of corneal tissue ofgenerally uniform thickness. When utilizing an applanation lens device,the Z-axis depth value is typically set at 160 μm below the proximalsurface of the lens contacting the cornea.

[0079] Without the use of an applanation lens or similar device, thecornea will be generally spherical. Instead of a constant depth value tocreate the resection to achieve a generally uniform thickness ofresected corneal tissue, the Z-axis depth value will have to becontrolled by the software. The eye should be fixed in a staticposition. A device to read the symmetry and dimensions of the eye, maybe used to determine appropriate X-axis depth values. The Z-axis depthvalue will be varied through the resection to achieve a resection ofcorneal tissue of generally uniform thickness.

[0080] For the raster pattern, the laser beam photodisrupts tissue in alinear path from the highest point on the X-axis to the lowest point onthe X-axis. The laser focal point is moved based on the spot separationvalue. The spot separation is preferably set such that the laser beamfocus provides overlapping areas of photodisruption.

[0081] The focal point for photodisruption is then incrementally movedto a lower X-axis location based on the line separation value. This timethe laser is positioned at the lowest point on the X-axis within thegeometric border for the new Y-axis location. The laser continuesthrough the X/Y-axis moving up the X-axis, then moving to a new Y-axislocation, then moving down the X-axis. Once the line reaches the lowestX-axis value of the geometric border, then the photodisruption stops.

[0082] If a peripheral reservoir is desired, a series of pulses may bedelivered before or after the raster pattern (or any other pattern) isdelivered in any peripheral shape or orientation and with any specificinternal parameters (spot, line separation, energy) to controlgas/debris accumulation and movement as well as tissueresection/separation and surface characteristics.

[0083] For a vertical resection (side cut), the laser beam is focusedwithin or near the circumference of the geometric border. Typically, thelaser beam is focused 50 μm from the circumference. The Z-axis (ordepth) of the laser focus is set at a position to focus the laser beamslightly below (typically 20 μm) the plane of the horizontal resection.The computer directs the laser beam in a path that follows thecircumference of the geometric border. The speed with which the laserfocus traverses the circle depends on the desired spot separationbetween focused pulses of light. Typically, for a circular border, thelaser traverses the circumference in a counter-clockwise fashion whenviewed from the user's perspective. The laser source issues a sequenceof pulses into the circumference that inscribes the horizontalresection. When the circle is complete, the Z-axis of the laser focus isrepositioned to a depth slightly above the initial Z-axis depth value.The laser then traverses the circumference following the same path asbefore and photodisrupts another layer of corneal tissue. This processis repeated until the surface of the cornea has been photodisrupted.Preferably, if using an applanation contact lens to flatten the cornea,the process continues to a few microns into the applanation contactlens. Utilizing concentric circles for the side cut creates a peripheraledge that is generally perpendicular to the X-Y axis.

[0084] Alternatively, the side cut may be made with incrementallyincreasing or decreasing circumferences of the geometric border. Forexample, given a circular geometric border, a first circularphotodisrupted cut may be made at the anterior interior surface of thehorizontal resection. Next, a second circular photodisrupted cut may bemade with an increased radius at a shallower depth. Ever-increasingradii cuts at incrementally shallower depths are made until the side cutis created through the surface of the cornea. This type of cut wouldcreate a sloping peripheral edge with an angle greater than 90 degrees.In other words, the outermost circular cut at the surface of the corneawould be greater in its radius than would be the initial cut made withinthe corneal tissue.

[0085] Another way to make the cut is by incrementally decreasing thegeometric border. In this case, a first concentric circular cut is made.The next cut would be shorter in radius than the first cut. Everdecreasing radii cuts are made, which creates a sloping peripheral edgewith an angle less than 90 degrees.

[0086] Also, with the creation of vertically displaced circles ofphotodisrupted tissue, the radius of each successive circle may beincrementally increased by a fixed amount until the maximum radius ofthe vertical resection is reached.

[0087] The hinge is that part of the circumference of the geometricborder where no cutting is performed. Preferably the reservoir iscreated near the location of the hinge. The laser beam is directed alongthe circumference of the geometric border. However, a continuous portionof the border is designated for the flap. No photodisruption occursalong the border designated a flap. For example, with a circulargeometric border, the hinge is an arc defined by its position and angle.When the laser focus reaches a predetermined position along its circularpath, the laser beams movement stops and reverses the path of the laserbeam with the next circle above the previous circle. This is done foreach circle comprising the vertical resection. In this manner, a portionof the vertical resection is masked, thereby creating a flap hinge. Inthe preferred embodiment, the reservoir angle and the hinge angle aresubstantially the same.

[0088] While the particular System and Method for Improved MaterialProcessing Using a Laser Beam as herein shown and disclosed in detail isfully capable of obtaining the objects and providing the advantagesherein before stated, it is to be understood that it is merelyillustrative of the presently preferred embodiments of the invention andthat no limitations are intended to the details of the construction ordesign herein shown other than as defined in the appended claims.

What is claimed is:
 1. A method for creating an anterior internalsurface and a posterior internal surface in a cornea of an eye, themethod comprising the steps of: directing a focal point of a laser beamand photodisrupting tissue to create a reservoir; directing the focalpoint of the laser beam at a starting point and photodisrupting tissueat the starting point; and moving the focal point of the laser beam fromthe starting point along a predetermined path to a plurality oflocations and photodisrupting tissue at the locations to form ananterior internal surface and a posterior internal surface, wherein saidsurfaces have a predetermined circumference.
 2. The method of claim 1,wherein the step of moving the focal point of the laser beam includesmoving the focal point of the laser beam along a predetermined path inthe shape of a raster pattern that runs back-and-forth through stromaltissue located inside the predetermined circumference from the startingpoint to an ending point located on the opposite side of thepredetermined circumference.
 3. The method of claim 1, wherein the stepof moving the focal point of the laser beam includes moving the focalpoint of the laser beam along a predetermined path in the shape of aspiral pattern that runs through stromal tissue located inside thepredetermined circumference from the starting point to a center of thepredetermined circumference.
 4. The method of claim 1, wherein the stepof moving the focal point of the laser beam includes moving the focalpoint of the laser beam along a predetermined path in the shape of aseries of concentric circles that runs through stromal tissue locatedinside the predetermined circumference from the starting point to thecenter of the predetermined circumference.
 5. The method of claim 1,further including the step of forming a peripheral surface that extendsat an angle from the posterior internal surface to the outer surface ofthe cornea, the peripheral surface being formed by moving the focalpoint of the laser beam and photodisrupting tissue at a plurality ofpoints along a path that runs from the vicinity of the outer surface ofthe cornea to the anterior internal surface.
 6. The method of claim 5,wherein the step of forming a peripheral surface includes forming theperipheral surface at an angle of greater than 90 degrees relative tothe posterior internal surface.
 7. The method of claim 5, wherein thestep of forming a peripheral surface includes forming the peripheralsurface at an angle of less than 90 degrees relative to the posteriorinternal surface.
 8. The method of claim 5, wherein the step of forminga peripheral surface includes moving the focal point of the laser beamand photodisrupting tissue along a path that is less than thepredetermined circumference in order to form a section of undisruptedtissue that acts as a hinge such that the anterior internal surface maybe lifted, but will still remain attached to the cornea.
 9. The methodof claim 8, wherein said hinge is located adjacent to the reservoir. 10.The method of claim 1, wherein the step of moving the focal point of thelaser beam includes leaving an undisrupted portion of stromal tissuealong the predetermined circumference for forming a hinge in order tomaintain contact between the anterior internal surface and the corneawhen the posterior internal surface is exposed.
 11. The method of claim1, wherein the step of moving the focal point of the laser beam includesdirecting the focal point of the laser beam around the entirepredetermined circumference of the internal surfaces so that theanterior internal surface can be completely removed from the cornea whenthe posterior internal surface is exposed.
 12. The method of claim 1,wherein the starting point is located beneath the outer surface of thecornea.
 13. The method of claim 1, wherein the starting point is locatedon the outer surface of the cornea.
 14. The method of claim 1, whereinthe predetermined path is shaped such that the predeterminedcircumference is generally circular in shape.
 15. The method of claim 1,wherein the predetermined path is shaped is shaped such that thepredetermined circumference is generally oval in shape.
 16. The methodof claim 1, wherein the predetermined path is shaped such that theanterior internal surface is generally planar.
 17. The method of claim1, wherein the predetermined path is such that the anterior internalsurface is generally convex.
 18. The method of claim 1, wherein thepredetermined path is such that the anterior internal surface isgenerally concave.
 19. The method of claim 1, wherein the reservoir isperipheral to the anterior internal surface and posterior internalsurface.
 20. The method of claim 1, wherein the reservoir is directlyconnected to a corneal-scleral junction of the eye.
 21. The method ofclaim 1, wherein the reservoir is connected to a corneal-scleraljunction of the eye via exiting channels.
 22. The method of claim 1,wherein the reservoir is connected to a corneal-scleral junction of theeye via potential corneal channels.
 23. The method of claim 1, whereinthe reservoir is created at a shallower depth relative to the ananterior internal surface and a posterior internal surface.
 24. Themethod of claim 1, wherein the reservoir is created at a deeper depthrelative to the anterior internal surface and the posterior internalsurface.
 25. The method of claim 1, wherein the reservoir is created ina central location of the posterior internal surface.
 26. The method ofclaim 1, wherein the reservoir is created by photodisruption withvariable laser pulse energies and/or separations to control gas/liquidand debris accumulation.
 27. The method of claim 1, wherein thereservoir is created by photodisruption with variable shape dimensionsto control gas/liquid and debris accumulation.
 28. The method of claim1, further comprising the step of creating one or more additionalreservoirs in the corneal tissue adjacent to the predeterminedcircumference.
 29. The method of claim 1, further comprising further thestep of creating passageways by photodisrupting corneal tissue from thereservoir to the predetermined circumference.
 30. The method of claim 1,further comprising repeating the moving step.
 31. The method of claim30, wherein repeating the moving step utilizes different laserparameters than the first moving step.
 32. The method of claim 1,further comprising moving the focal point of the laser beam along adifferent predetermined path to a plurality of locations andphotodisrupting tissue at the locations.
 33. The method of claim 1,further comprising removing at least a portion of the corneal layer toexpose the anterior internal surface and posterior internal surface ofthe cornea.
 34. The method of claim 1, wherein the starting point is inthe vicinity of the predetermined circumference.
 35. The method of claim1, wherein the reservoir is created adjacent to the predeterminedcircumference.
 36. A computer-implemented method for directing a laserbeam to create a resected area of corneal tissue, said methodcomprising: receiving a selection for a geometric border; orienting thegeometric border about a display of a cornea, the geometric borderhaving a predetermined circumference; receiving a selection for a typeof pattern cut; directing the laser beam to perform photodisruption ofcorneal tissue to create a reservoir; and directing the laser beam toperform photodisruption of corneal tissue using the selected pattern cutfor the selected geometric border, wherein the pattern cut forms ananterior internal surface and a posterior internal surface of thecorneal tissue.
 37. The computer-implemented method of claim 36, furthercomprising determining a central point of the cornea for positioning thecircumference of the geometric border about the cornea.
 38. Thecomputer-implemented method of claim 36, wherein the cornea has an outersurface and the photodisruption is performed at a selected depth belowthe corneal surface.
 39. The computer-implemented method of claim 36,wherein the type of pattern cut is spiral.
 40. The computer-implementedmethod of claim 36, wherein the type of pattern cut is concentric. 41.The computer-implemented method of claim 36, wherein the type of patterncut is rasterized.
 42. The computer-implemented method of claim 36,wherein the directing a laser beam to perform photodisruption of cornealtissue forms a horizontal resection.
 43. The computer-implemented methodof claim 42, further comprising the step of directing the a laser beamto perform photodisruption of corneal tissue to create a verticalresection about the horizontal resection.
 44. The computer-implementedmethod of claim 36, wherein the reservoir is peripheral to the anteriorinternal surface and the posterior internal surface.
 45. Thecomputer-implemented method of claim 36, wherein the reservoir isdirectly connected to a corneal-scleral junction of the eye.
 46. Thecomputer-implemented method of claim 36, wherein the photodisruption ofcorneal tissue using the selected pattern cut begins near the vicinityof the predetermined circumference.
 47. The computer-implemented methodof claim 36, wherein the reservoir is connected to a corneal-scleraljunction of the eye via exiting channels.
 48. The computer-implementedmethod of claim 36, wherein the reservoir is connected to acorneal-scleral junction of the eye via potential corneal channels. 49.The computer-implemented method of claim 36, wherein the reservoir iscreated at a shallower depth relative to the an anterior internalsurface and a posterior internal surface.
 50. The computer-implementedmethod of claim 36, wherein the reservoir is created at a deeper depthrelative to the an anterior internal surface and a posterior internalsurface.
 51. The computer-implemented method of claim 36, wherein thereservoir is created in a central location of the posterior internalsurface.
 52. The computer-implemented method of claim 36, wherein thereservoir is created with variable laser pulse energies and/orseparations to control gas/liquid and debris accumulation.
 53. Thecomputer-implemented method of claim 36, wherein the reservoir iscreated by photodisruption with variable shape dimensions to controlgas/liquid and debris accumulation.
 54. The computer-implemented methodof claim 36, further comprising the step of creating one or moreadditional reservoirs in the corneal tissue adjacent to the geometricborder.
 55. The computer-implemented method of claim 36, furthercomprising the step of creating passageways by photodisrupting cornealtissue from the reservoir to the geometric border.
 56. Thecomputer-implemented method of claim 36, further comprising repeatingthe step of directing the laser beam to perform photodisruption ofcorneal tissue using the selected pattern cut.
 57. Thecomputer-implemented method of claim 56, wherein the repeated movingstep utilizes different laser parameters than the first moving step. 58.The computer-implemented method of claim 36, further comprising rotatingthe selected pattern cut and directing the laser beam to performphotodisruption of the corneal tissue using the rotated pattern cut. 59.The computer-implemented method of claim 36, further comprisingselecting a second pattern cut and directing the laser beam to performphotodisruption of the corneal tissue using the second pattern cut. 60.A method for controlling gas and debris accumulation when creating ananterior internal surface and a posterior internal surface in tissueutilizing a laser beam comprising the steps of: creating a reservoir incorneal tissue by photodisrupting an amount of corneal tissue; andcreating a main pattern cut by photodisrupting an amount of cornealtissue adjacent to said reservoir, whereby an anterior internal surfaceand a posterior internal surface of the main pattern cut is formed. 61.The method of claim 60, wherein the reservoir is peripheral to theanterior internal surface and posterior internal surface.
 62. The methodof claim 60, wherein the reservoir is directly connected to acorneal-scleral junction of the eye.
 63. The method of claim 60, whereinthe reservoir is connected to a corneal-scleral junction of the eye viaexiting channels.
 64. The method of claim 60, wherein the reservoir isconnected to a corneal-scleral junction of the eye via potential cornealchannels.
 65. The method of claim 60, wherein the reservoir is createdat a shallower depth relative to the anterior internal surface and theposterior internal surface.
 66. The method of claim 60, wherein thereservoir is created at a deeper depth relative to the anterior internalsurface and the posterior internal surface.
 67. The method of claim 60,wherein the reservoir is created in a central location of the posteriorinternal surface.
 68. The method of claim 60, wherein the reservoir iscreated by photodisruption with variable laser pulse energies and/orseparations to control gas/liquid and debris accumulation.
 69. Themethod of claim 60, wherein the reservoir is created by photodisruptionwith variable shape dimensions to control gas/liquid and debrisaccumulation.
 70. The method of claim 60, further comprising creatingone or more additional reservoirs in the corneal tissue byphotodisrupting an amount of corneal tissue.
 71. The method of claim 60,wherein the main pattern cut has a circumference, and the reservoircircumscribes the circumference of the main pattern cut.
 72. The methodof claim 60, wherein the main pattern cut has a circumference, andfurther comprising creating passageways by photodisrupting cornealtissue from the reservoir to the circumference of the main pattern cut.73. The method of claim 60, further comprising repeating the step ofcreating a main pattern cut.
 74. The method of claim 73, wherein therepeating step is performed utilizing different laser parameters. 75.The method of claim 60, further comprising the step of creating a secondpattern cut by photodisrupting an amount of corneal tissue.
 76. A methodfor controlling gas and debris accumulation in a material, said methodcomprising the steps of: creating a reservoir within said material byphotodisrupting an amount of material; and creating a main pattern cutby photodisrupting an amount of material adjacent to said reservoir,whereby an anterior internal surface and a posterior internal surface ofthe main pattern cut is formed.
 77. The method of claim 76, wherein thematerial is mammalian tissue.
 78. The method of any one of claims 76 and77, wherein the reservoir is created peripheral to the anterior internalsurface and the posterior internal surface.
 79. The method of any one ofclaims 76 and 77, wherein the reservoir is created at a shallower depthrelative to the anterior internal surface and the posterior internalsurface.
 80. The method of any one of claims 76 and 77, wherein thereservoir is created at a deeper depth relative to the anterior internalsurface and the posterior internal surface.
 81. The method of any one ofclaims 76 and 77, wherein the reservoir is created in a central locationof the posterior internal surface.
 82. The method of any one of claims76 and 77, wherein the reservoir is created by photodisruption withvariable laser energies and/or separations to control gas/liquid anddebris accumulation.
 83. The method of any one of claims 76 and 77,wherein the reservoir is created by photodisruption with variable shapedimensions to control gas/liquid and debris accumulation.
 84. The methodof any one of claims 76 and 77, wherein the main pattern cut has acircumference and the reservoir circumscribes the circumference of themain pattern cut.
 85. The method of any one of claims 76 and 77, whereinthe main pattern cut has a circumference and further comprising creatingpassageways by photodisrupting material from the reservoir to thecircumference.
 86. The method of any one of claims 76 and 77, whereinthe main pattern cut has a predetermined circumference and the creatingstep begins at a starting point in the vicinity of the predeterminedcircumference.
 87. The method of any one of claims 76 and 77, furthercomprising repeating the step of creating a main pattern cut.
 88. Themethod of any one of claims 76 and 77, further comprising the step ofcreating a second pattern cut by photodisrupting an amount of material.89. A method for improved material processing using a laser beamcomprising the steps of: directing a laser beam focal point at or belowthe surface of a material; moving the laser beam focal point in aprimary pattern of photodisruption of the material; and moving the laserbeam focal point in one or more secondary patterns specific to thematerial to reduce or mitigate the accumulation or effects of gas,debris, fluid, or other by-products of photodisruption either at alocation where additional laser pulses are being placed or in othersensitive locations in the material.
 90. The method in 89, wherein thematerial is inorganic.
 91. The method in 89, wherein the material isorganic.
 92. The method in 89, wherein the material is a tissue.
 93. Themethod in 89, wherein the material is an eye.
 94. The method in 93,wherein the material is a cornea of the eye.
 95. The method in 89,wherein the one or more secondary patterns includes a reservoir adjacentor connected to the primary pattern.
 96. The method in 89, wherein theone or more secondary patterns include a connection to an existingreservoir in the material adjacent or connected to the primary pattern.97. The method in 89, wherein the laser beam has pulse characteristics,and the laser pulse characteristics include spot separation between 2-20microns in the primary and/or secondary patterns.
 98. The method in 89,wherein the laser beam has pulse characteristics, and the pulsecharacteristics for the primary pattern include laser pulse energybetween 1-10 μJ.
 99. A computer-based system for directing a laser beamto create a resected area of corneal tissue, the system comprising: aninput control device; memory for storing information received from saidinput control device; a processor unit coupled to the input controldevice and to the memory for processing the information; an outputdisplay for displaying information; a laser source for generating alaser beam; a focusing mechanism coupled electromechanically to theprocessor unit, and a software program operable with said processorunit, said software program configured for performing the steps of:positioning a laser beam focal point and photodisrupting tissue tocreate a reservoir, positioning a laser beam focal point at a startingpoint in the vicinity of an outer edge of the internal surface to beexposed and photodisrupting tissue at said starting point, and movingthe laser beam focal point from the starting point along a predeterminedpath and photodisrupting tissue at spots along said path for creating apattern of interconnected spots across the surface to be exposed to forma layer of resected corneal tissue.
 100. The computer-based system ofclaim 99, wherein said step of moving the focal point of the laser beamincludes moving the focal point of the laser beam along a predeterminedpath in the shape of a raster pattern that runs back-and-forth throughstromal tissue located inside the predetermined circumference from thestarting point to an ending point located on the opposite side of thepredetermined circumference.
 101. The computer-based system of claim 99,wherein said step of moving the focal point of the laser beam includesmoving the focal point of the laser beam along a predetermined path inthe shape of a spiral pattern that runs from through stromal tissuelocated inside the predetermined circumference from the starting pointto the center of the predetermined circumference.
 102. Thecomputer-based system of claim 99, wherein said step of moving the focalpoint of the laser beam includes moving the focal point of the laserbeam along a predetermined path in the shape of a series of concentriccircles that runs through stromal tissue located inside thepredetermined circumference from the starting point to the center of thepredetermined circumference.
 103. The computer-based system of claim 99,wherein the software further performs step of forming a peripheralsurface that extends at an angle from the internal surface to the outersurface of the cornea, said peripheral surface being formed by movingthe focal point of the laser beam and photodisrupting tissue at aplurality of points along a path that runs from the vicinity of theouter surface of the cornea to the internal surface.
 104. Thecomputer-based system of claim 103, wherein the step of forming aperipheral surface includes forming said peripheral surface at an angleof greater than 90 degrees relative to the internal surface.
 105. Thecomputer-based system of claim 103, wherein the step of forming aperipheral surface includes forming said peripheral surface at an angleof less than 90 degrees relative to the internal surface.
 106. Thecomputer-based system of claim 103, wherein the step of forming aperipheral surface includes moving the focal point of the laser beam andphotodisrupting tissue along a path that is less than the predeterminedcircumference in order to form a section of undisrupted tissue that actsas a hinge such that the corneal layer may be lifted, but will stillremain attached to the cornea.
 107. The computer-based system of claim99, wherein the step of moving the focal point of the laser beamincludes leaving an undisrupted portion of stromal tissue along thepredetermined circumference for forming a hinge in order to maintaincontact between the corneal layer and the cornea when the internalsurface is exposed.
 108. The computer-based system of claim 99, whereinthe step of moving the focal point of the laser beam includes directingthe focal point of the laser beam around the entire predeterminedcircumference of the internal surface so that the corneal layer can becompletely removed from the cornea when the internal surface is exposed.109. The computer-based system of claim 99, wherein said starting pointis located beneath the outer surface of the cornea.
 110. Thecomputer-based system of claim 99, wherein said starting point islocated on the outer surface of the cornea.
 111. The computer-basedsystem of claim 99, wherein the predetermined path is shaped such thatthe predetermined circumference is generally circular in shape.
 112. Thecomputer-based system of claim 99, wherein the predetermined path isshaped is shaped such that the predetermined circumference is generallyoval in shape.
 113. The computer-based system of claim 99, wherein thepredetermined path is shaped such that the internal surface is generallyplanar.
 114. The computer-based system of claim 99, wherein thepredetermined path is such that the internal surface is generallyconvex.
 115. The computer-based system of claim 99, wherein thepredetermined path is such that the internal surface is generallyconcave.